The problem is not there in twentyEleven so I am pretty sure its theme related and not plugin related.
It's not browser specific and it happens in all the major browers.
I did fix the problem on the current year by adding placeholder events. To see the issue switch the year to 2013 for any month
I have verified on my end that when their is no date in a month extra markup gets added by something to the control bar area.
I understand that the problem is most likely happening due to something in the themes code but the below users is having the same issue so perhaps not? I appreciate any assistance you do provide as its above the call of duty and thank you for that
I am glad I found that post I was at least able to apply a band aid once I figured out it was happening only when there is no event in the month